Increasing incidence and prevalence of ANCA-associated vasculitis in Northern Norway

Objective. ANCA-associated vasculitides (AAV) have increased in prevalence since the 1980s. We aimed to investigate the incidence and prevalence of AAV during a 15-year period from 1999 to 2013 in Northern Norway, looking for variations during this period. Methods. Patient records were retrieved from The Northern Norwegian Vasculitis Registry; in addition we searched all regional hospital databases. Patients diagnosed with AAV from 1999 through to 2013 were included. For prevalence data, patients residing in the area, but with AAV diagnosis prior to 1999, were also included. The diagnosis of AAV was based on the European Medicines Agency algorithm. Results. We identified 140 cases; 88 were classified as granulomatosis with polyangiitis (GPA), 37 as microscopic polyangiitis (MPA) and 15 as eosinophilic granulomatosis with polyangiitis (EGPA). Adult (age >= 15 years) annual incidence rates per million were as follows: for GPA 15.6 (95% CI: 12.5, 19.2), MPA 6.5 (95% CI: 4.6, 9.0), EGPA 2.7 (95% CI: 1.5, 4.5) and overall AAV 24.7 (95% CI: 20.8, 29.2). Incidences of MPA and overall AAV showed an increasing trend (P < 0.05). Adult point prevalence rates per million in 2013 were 261 (95% CI: 213, 316) for GPA, 58.2 (95% CI: 36.9, 87.3) for MPA, 32.9 (95% CI: 17.5, 56.3) for EGPA and 351 (95% CI: 296, 416) for overall AAV. Conclusion. The incidence rate of GPA and the prevalence rates of GPA and EGPA are currently the highest reported. MPA increased significantly from a prior low incidence. The overall AAV annual incidence and prevalence are still increasing.